1. Field of the Invention
The present invention relates to generally a speed regulation system for brushless DC motors and more particularly a speed regulation system for DC motors with Hall generators of the type in which the supply of the driving current to the stator windings is switched in response to the angular position of the rotor made of permanent magnet which is detected by the Hall generators, the speed regulation system comprising means for detecting the frequency of the alternating output voltages of the Hall generators representing the rotational speed of the rotor so as to generate the pulse signals representing the frequency of the alternating output signals, and an oscillator which is triggered in response to the pulse signals from the detecting means so that the output signals with a desired waveform may be applied through switching means and a driving circuit to the stator windings of the DC motor.
2. Description of the Prior Art
There has been known a DC motor with Hall generators of the type in which in response to the output Hall voltages of Hall generators which are so disposed as to detect the angular position of a rotor a transistorized driving circuit supplies the driving current to stator windings. The waveform of the driving current is in general sinusoidal, but other waveforms may be used, and the phase of the driving current is dependent upon the positions of the Hall generators on the stator. Since the phase of the driving current relative to the stator windings is determined in the assembly step, the torque with the maximum efficiency cannot be obtained. Furthermore it is extremely difficult to form a waveform of the driving current so as to obtain the maximum torque.